GB2329528A

GB2329528A - Multi phase machine having phase unbalance compensated by cooling

Info

Publication number: GB2329528A
Application number: GB9816892A
Authority: GB
Inventors: Helmut Kreuzer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-08-09
Filing date: 1998-08-03
Publication date: 1999-03-24
Anticipated expiration: 2018-08-03
Also published as: GB2329528B; FR2767236B1; DE19734592C1; ES2148087A1; GB9816892D0; ES2148087B1; FR2767236A1

Abstract

The electrical machine, in particular a three-phase generator, with a stator winding (12) consisting of winding wire and disposed in the stator core (10) of the machine, has the special feature of the phases (14 to 16) of the stator winding (12) being wound with different slot space factors and the resulting load unbalance being compensated by appropriately cooling the phases.

Description

2329528 1 Electrical machine. in particular a three-12hase machine

Prior art

The invention is based on an electrical machine, in particular a threephase machine, according to the type of the main claim. The stator winding of machines of this kind is of a symmetrical structure, which is achieved through uniform conductor cross sections and a uniform number of conductors. However this has the disadvantage that, although the socalled slot space factor is equal in all the slots, it is not optimum on account of the crossing end connections.

Advantages of the invention In contrast the electrical machine according to the invention, in particular a threephase machine with the characterising features of the main claim has the atage of enabling the imbalance of the phases in the stator core with respect to load and cooling to be compensated, in spite of different conductor croks sections or a difFerent number of conductors in the three phases. The achievement of a higher slot space factor than has been achieved until now, of an increase in power and efficiency and a reduction in noise is of considerable importance. The invention can be applied to electric motors and generators of any type.

Further advantages of the invention will emerge from the subclainis and the following description and drawings.

Drawings An embodiment of the invention is reproduced mi the drawings, Figure 1 of which 2 is a diagrammatic view of the stator core with stator winding and Figure 2 a side view according to Figure 1.

Description of the embodiment

The number 10 in Figures 1 and 2 designates a stator core of a threephase generator for motor vehicles which comprises thirty six axially extending slots 11 and is formed in a known manner as a laminated core. The stator winding is disposed in the stator core or in the slots. As this is a threephase machine, the stator winding consists of three phases 14 to 16, which are formed in a very special way. The first phase 14 lies in the bottom of the slot and therefore furthest to the outside in the radial direction. Seven conductors per slot 11 are provided as turns, for example, with a slot space factor of 49 % being achieved. The second phase 15, which comprises eight conductors per slot 11 as turns and has a slot space factor of 45 %, lies further inward in the radial direction and staggered Mi relation to the phase 14. The third phase 16, which has nine conductors per slot as turns and a slot space factor of 41 %, lies furthest to the inside.

The wire is thickest in the first phase, e.g. it has a cross section of 1. 65 MM2, it is thinner mi the second, middle phase, with a cross section of 1.60 MM2, and is thinnest in the third phase, with a cross section of, e.g. 1.50 mm. It is obvious from this that the three phases of the stator windmig are unbalanced with respect to voltage, current and heat load because of the special formation. The voltage imbalances are compensated by a bridge rectifier at the generator output and the unbalance of the load is largely compensated by the differing arrangement of the phases in the slots of the stator core 10. This is achieved by 'making the cooling the least egective in the first phase 14, although this has the lowest resistance, so that the smallest heat losses occur here. The most effective cooling is in the inner 1 3 phase 16, although this has the highest resistance and thus the greatest heat losses. The fans for compact three-phase generators are provided internally at the front,_:thd of the rotor. The cooling air is taken in axially on both sides and forced radially through the end connections. Cooling is therefore most intensive at phase 16. The overall result is thus an average slot space factor of 45 %, which is approximately 5 % higher than the factors usually obtained until now.

In addition to the stator core 10 and the stator winding 12, Figure 2 shows the insulating insert 18 as well as the three phase connections 19wx, 20v-y and 2 lw-z. In Figure 1 - this should also be noted - the position of the winding strands is shown diagrammatically.

In a modification of the embodiment it is also possible, within the scope of the invention, to achieve an improved slot space factor by making just the numbers of conductors or just the conductor cross sections different for the three phases, with the outer phase 14 in each case having the greatest number of conductors or the thickest conductor cross section and the inner phase 16 having the smallest number of conductors or the smallest conductor cross section.

4

Claims

1. Electrical machine, in particular a three-phase generator, with a preferably three-phase stator winding (12) consisting of winding wire and disposed in slots in the stator core of the machine, characterised mi that the phases (14, 15, 16) of the stator winding (12) are wound with different slot space factors and the resulting load unbalance is compensated by means of varymg cool Mig of the phases.

2. Electrical machine according to claim 1, characterised in that the conductor cross section is of a different magnitude in the different phases.

Electrical machine according to claim 1, characterised in that the number of conductors for each phase is different.

4. Electrical machine according to one of claims 1 to characterised m that the conductor cross section and the number of conductors in the phases is different, such that the outer phase (14) has the highest and the inner phase (16) the lowest slot space factor.

5. Electrical machine according to one of claims 1 to 4, characterised in that the outer phase (14) has the greatest conductor cross section and the smallest number of conductors and the inner phase (16) has the smallest conductor cross section and the greatest number of conductors.

6. Electrical machine according to claim 1, characterised in that the outer phase (14) has the greatest number of conductors or the greatest conductor cross section and that the inner phase (16) has the smallest number of conductors 1 or the smallest conductor cross section.

7. An electrical machine substantially as herein described with reference to the accompanying drawing.